1. Technical Field
The present invention relates to a lens positioning jig which is used for attaching a lens barrel to a housing, a method of attaching a lens barrel using the lens positioning jig, and a lens device in which the lens barrel is attached to the housing in accordance with the lens positioning jig and the method of attaching the lens barrel.
2. Related Art
As a large-screen monitor, a rear projection device is known. The rear projection device includes a screen which is mounted to a housing, a plane mirror which is mounted to a position in rear of the screen, and an optical engine which projects image light to the plane mirror. The optical engine includes an illumination optical system which generates uniform illumination light from a high brightness light source, a color separating/synthesizing optical system which separates the illumination light into three colors and then synthesizes the resultant after granting image information thereto using an image display element, and a projection lens unit which enlarges and projects the image light, which is formed in this way, to the plane mirror.
The projection lens unit includes a convergent optical system which converges the image light being incident from the color separating/synthesizing optical system, a mirror which reflects the image light converged by the convergent optical system, a projection optical system which enlarges the image light reflected by the mirror and which projects the image light to a plane mirror, and a lens housing in which they are incorporated (for example, see Patent Documents 1 (JP-A-2005-352293 corresponding to US-A-2005-275759)).
The convergent optical system is configured such that a plurality of convergent lenses are mounted inside the lens barrel, the lens barrel being attached to a barrel attachment portion disposed in one end of the lens housing. Additionally, in order to converge appropriately the image light which is incident to the mirror without a change, a part of the lens constituting the convergent optical system may be mounted to a second lens barrel and the second lens barrel may be disposed between the mirror and a first lens barrel which is attached to one end of the lens housing.
In such a convergent optical system, when a gap occurs between optical axes of the first lens barrel and the second lens barrel, image quality deteriorates. For this reason, the known projection lens unit improves forming precision of an attachment portion to be attached with the second lens barrel with respect to the barrel attachment portion to be attached with the first lens barrel and then aligns the optical axis center to be the same when the second lens barrel is attached to the attachment portion. Alternatively, for example, like a lens device disclosed in Patent Document 2 (JP-A-2001-100071), the lens barrel comes into contact with a plurality of set screws and then the optical axis is adjusted by fastening or unfastening the respective screws.
However, when the lens housing and the second lens barrel are formed of plastic, a problem may arise in that it is not possible to obtain sufficient precision. Although additional machining processes may be carried out after the forming process, a problem may arise in that a cost increases.
In addition, when the optical axis is adjusted through the set screw, a problem may arise in that a deformation may occur in the lens or the barrel to thereby deteriorate image quality. Further, a problem may arise in that repeatability of a plurality of products is low and it takes time for adjusting the optical axis one time, thereby requiring an experienced skill to some degree.
The present invention solves the above-described problems, and an object of the invention is to provide a lens positioning jig, a method of attaching a lens barrel, and a lens device which can fix a lens barrel with high precision without forming a barrel attachment portion of a lens housing with high precision.